This invention relates to a new stabilizer composition for enhancing the resistance to deterioration upon heating of vinyl chloride polymers, and to vinyl chloride polymers having enhanced resistance to deterioration in initial color, heat stability and clarity as a result of incorporating therein a stabilizer composition according to this invention.
There is a voluminous literature on the stabilization of vinyl chloride polymers. Patent disclosures of materials stated to be useful in minimizing deterioration of vinyl chloride polymers on heating number well over one thousand. Among the more important heat stabilizers in commercial use are mild alkalis such as sodium carbonate, disodium phosphate, and sodium and potassium salts of partially esterified phosphoric acids; carboxylates and phenolates of zinc, cadmium, and the alkaline earth metals; inorganic and organic lead salts; organotin carboxylates, as disclosed by Quattlebaum in U.S. Pat. No. 2,307,157; organotin mercaptides as disclosed by Leistner in U.S. Pat. Nos. 2,641,588 and 2,641,598; various metal-free organic compounds such as the polyols, e.g. mannitol, sorbitol, glycerol, pentaerythritol, organic phosphites, 1,2-epoxides, e.g., soybean oil epoxide, isooctyl epoxystearate, and the diglycidyl ether of 2,2-bis(p-hydroxyphenyl) propane, and nitrogen compounds, e.g., phenylurea, N,N'-diphenylthiourea, and 2-phenylindole. For detailed discussion of heat stabilizers for vinyl halide resins, reference may be made to the articles, L. I. Nass, in "Encyclopedia of Polymer Science and Technology" (N. Bikales, ed.) Vol. 12, pages 737 to 768 (1970); N. L. Perry "Barium-Cadmium Stabilization of Polyvinyl Chloride," Rubber Age 85 449-452 (June, 1959), and by H. Verity-Smith, British Plastics 27 176-179, 213-217, 307-311 (1954); the brochure by the same author The Development of the Organotin Stabilizer (Tin Research Institute, 1959) and the book La Stabilisation des Chlorures de Polyvinyle by F. Chevassus (Amphora, Paris, 1957).
C. F. Prutton in U.S. Pat. No. 2,224,695 of Dec. 10, 1940, disclosed mono-, di-, and tri-esters of phosphorous acid and derived salts as examples of inhibitors for protecting the surface of a metal to which the inhibitors are applied against oxidation and corrosion. Prutton's inhibitors are described as preferably of such nature that in contact with aqueous media they will yield a solution having a pH of below 7.
G. Denison Jr., in U.S. Pat. No. 2,346,155 of Apr. 11, 1944 disclosed a hydrocarbon oil containing a combination of stabilizing agents, comprising a thioether or seleno ether and an oxide, sulfide, or selenide having directly connected to an oxygen, sulfur or selenium atom both a metal in a basic form and an acid-forming element such as those of Periodic groups IIIA, IV, VB, and VIB to which is attached an organic substituent either directly or through an intervening atom. Denison's disclosure encompasses untold thousands of compounds in over 150 classes, of which 28 are classes of phosphorus compounds among which phosphorous acid monoesters and di-esters are mentioned in the form of metal salts.
J. McNab in U.S. Pat. No. 2,391,099 of Dec. 18, 1945 disclosed the use of mineral lubricating oils of a combination of two additives, the first being a metallic salt of an inorganic acid having at least one oil-solubilizing organic group and the second being an alkylated p-cresol. McNab's metallic salt can be derived from any of a large number of acids containing sulfur, phosphorus, or both, including diisobutylphenyl phosphorous acid (C.sub.8 H.sub.17 C.sub.6 H.sub.4 O).sub.2 (OH)P, with any metal, with salts of Group II stated to be particularly effective.
W. Leistner in U.S. Pat. No. 2,564,646 of Aug. 14, 1951 disclosed vinyl chloride polymer compositions containing polyvalent metal carboxylate stabilizers together with an alkyl or aryl phosphite anti-clouding agent, and in U.S. Pat. No. 2,716,092 of Aug. 23, 1955 disclosed the use of hydrocarbon-substituted phenol metal salts in vinyl chloride polymer stabilizers along with metal carboxylates and organic phosphites.
Additional representative disclosures of organic esters of phosphorous acid used in vinyl chloride polymer stabilizers are by F. Hansen in U.S. Pat. No. 2,867,594 of Jan. 6, 1959, J. Darby in U.S. Pat. No. 2,951,052 of Aug. 30, 1960, L. Friedman in U.S. Pat. No. 3,047,608 of July 31, 1962, R. Buckley in U.S. Pat. No. 3,342,767 of Sept. 19, 1967 and J. Scullin in U.S. Pat. No. 3,202,622 of Aug. 24, 1965.
W. Leistner in U.S. Pat. No. 2,997,454 of Aug. 22, 1961 disclosed polyvinyl chloride compositions of excellent initial color stabilized with a combination of an organic triphosphite with a heavy metal fatty acid salt to which there is added a phosphorus compound having at least one hydrogen atom of acidic character. The phosphorus acids in Leistner's compositions are defined by the formula:
__________________________________________________________________________ ##STR1## (V) ##STR2## In this formula, phosphorus has a valence of three or five, the additional two valences being indicated by dotted line bonds. Typical phosphorus acids coming within this gen- eral formula are the (VI)owing: ##STR3## (I) (a) ##STR4## (VII) ##STR5## (II) (a) ##STR6## (VIII) ##STR7## (III) (a) ##STR8## Pyrophosphoric acid (b) ##STR9## In the above formulae R.sub.1 and R.sub.2 represent an organic aliphatic, aromatic or nonaromatic alicyclic hydrocarbon or heterocyclic radical having from one to about thirty carbon atoms. R.sub.1 and R.sub.2 in I, II, III (a) and IV may be the same or different. (IV) Phosphonic acids (IV) ##STR10## __________________________________________________________________________
P. Klemchuk in U.S. Pat. No. 3,219,605 of Nov. 23, 1965 disclosed cadmium, barium, calcium, or zinc salts of monoalkyl phosphites are remarkably effective light stabilizers for polyvinyl chloride compositions, alone or in combination with other light and/or thermal stabilizers. The metal salts are defined by the formula: ##STR11## wherein R is an alkyl radical, e.g. alkyl having from 1 to 30 carbon atoms, preferably having from 1 to 12 carbon atoms, and
M is a divalent metal which may be cadmium, barium, calcium or zinc.
Farbwerke Hoechst in French Pat. No. 1,412,321 of Aug. 16, 1965 disclosed the stabilization against light of polyvinyl chloride with 0.1 to 5% by weight of nickel organic phosphites containing only nickel, phosphorus, carbon, hydrogen and oxygen, along with barium-cadmium soaps, organic phosphite, epoxy compounds, and optionally ultraviolet absorbers.
R. Harrington, Jr. in U.S. Pat. No. 3,274,014 of Sept. 20, 1966 disclosed yarn compositions of synthetic fibers having incorporated a small amount of a metal monoalkyl or monoaryl phosphate, metal dialkyl phosphate, metal alkyl phosphonate, metal alkyl (alkyl phosphonate) or metal dialkylphosphite are resistant to ultraviolet light. Examples show among others yarns spun from dopes of modified vinylidene chloride-acrylonitrile copolymer containing zinc diethyl phosphite.
G. Juredine in U.S. Pat. No. 3,284,386 of Nov. 8, 1966 disclosed organic metallophoshite stabilizers for vinyl chloride polymers represented by the formula ##STR12## in which M can be barium, calcium, and strontium and R and R" can be alky- groups, cycloaliphatic groups, aryl groups, aralkyl groups, alkaryl groups, and their halo substituted derivatives, R having from 4 to 18 and R" from 3 to 17 carbon atoms.
F. Kujawa in U.S. Pat. No. 3,412,118 of Nov. 19, 1968 disclosed phosphorous acid monoesters of 2,6-disubstituted and 2,4,6-trisubstituted phenols and their metal salts. Kujawa's monoesters have the formula ##STR13## wherein R is selected from the group, consisting of hydroxyl and halogen radicals, Y and Y' are organic radicals containing at least four carbon atoms, and Z is selected from the group consisting of hydrogen, halogen, and organic radicals containing at least four carbon atoms.
The metal salts of the primary aryl phosphites of this invention have the formulas: ##STR14## wherein Y and Y' are organic radicals containing at least four carbon atoms, Z is selected from the group consisting of hydrogen, halogen, and organic radicals containing at least four carbon atoms, X is selected from the group consisting of ammonium, substituted ammonium and metals, and n is an integer from 1 to 4 representing the valence of X. Two formulas have been illustrated to show that two forms of primary phosphites are believed to exist. However, Formula A will be used throughout this application as the presently preferred form.
In Kujawa metal salts, the molar ratio of phosphorous acid monoester groups to metal atoms is equal to the valence of the metal, so that for bivalent metals Kujawa teaches only salts in which there are two phosphorous acid monoester groups for each metal atom.
Kujawa points out prior art "primary aryl phosphites, including the corresponding salts, are too unstable to moisture to permit their general usage", while his aryl phosphites and salts are stable.